How many gigajoules are in 1 joule?

1 joule equals 1e-9 gigajoules, using the exact defined conversion factor rather than an estimate.

How do I convert joule to gigajoule?

Multiply the joule value by 1e-9. The converter above does this instantly to whatever precision you set.

How do I convert gigajoule back to joule?

Use the reverse factor: 1 gigajoule equals 1,000,000,000 joules. You can also use the swap control in the converter above to flip the direction instantly.

Gigajoule (GJ) is a unit of energy.

Is the joule to gigajoule conversion exact?

Yes. Both joule and gigajoule are defined by fixed standards rather than physical artifacts, so the factor of 1e-9 used above is exact to as many digits as you choose to display.

Joules to Gigajoules Converter

Q: What is a joule?

Joule (J) measures energy. The joule is the SI derived unit of energy, defined as the work done by one newton acting over one meter. It is classified as a SI derived unit.

About Converting Joules to Gigajoules

Joule and Gigajoule both measure energy, and the conversion is especially useful for comparing nutrition labels (kilocalories) against scientific energy figures (joules). Joule is most often used for physics and engineering energy calculations.

Formula

gigajoules = joules × 1e-9

This factor comes from each unit's defined relationship to the category's base unit: 1 joule equals 1 base unit, and 1 gigajoule equals 1000000000 base units, so dividing one by the other gives the direct joule-to-gigajoule factor of 1e-9.

Simple example

1 J × 1e-9 = 1e-9 GJ

1 joule = 1e-9 gigajoules.

Real-world example

100 J × 1e-9 = 1e-7 GJ

100 joules = 1e-7 gigajoules.

Conversion table

Joule (J)	Gigajoule (GJ)
1 J	1e-9 GJ
10 J	1e-8 GJ
100 J	1e-7 GJ
500 J	5e-7 GJ
1,000 J	0.000001 GJ
2,000 J	0.000002 GJ

Reverse conversion: Gigajoule to Joule

1e-9 GJ × 1000000000 = 1 J

1e-9 gigajoules = 1 joule.

joules = gigajoules × 1000000000

For a page dedicated to this direction, see Gigajoule to Joule.

Understanding the Joule

Joule (J) measures energy. The joule is the SI derived unit of energy, defined as the work done by one newton acting over one meter. It is classified as a SI derived unit.

Where it's used: Standard scientific and engineering energy unit worldwide

Uses of the Joule today

Physics and engineering energy calculations
Electrical energy in scientific contexts (though kWh is used for billing)
Nutrition labeling in some countries (alongside or instead of calories)

History of the Joule

The joule is named after English physicist James Prescott Joule, whose experiments in the 1840s established the mechanical equivalent of heat — demonstrating that mechanical work and heat are interchangeable forms of energy, foundational to the first law of thermodynamics.

The unit itself was formally adopted as the SI derived unit of energy by international agreement as part of the broader SI system, defined coherently from the base units (kg, m, s) rather than as an independent physical standard.

Historical origin. Joule was not the invention of a single named person; it developed through the process described above.

Understanding the Gigajoule (GJ)

Gigajoule is 1000000000 joule units.

Joule — sources

BIPM SI Brochure — Coherent derived units — Defines the joule as the SI unit of energy.

Joules to Gigajoules Converter — J to GJ

Energy Converter